JP2000159088A - Resin piston for master cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform the assembling of a retainer with a minimum reduction in strength and keep the function by arranging the engaging groove to be formed on the circumferential part of a cylindrical part for the engagement of the retainer in two or more circumferential positions of the cylindrical part. SOLUTION: A retainer 11 has two claw parts 11a bent radially inward, and it is locked by engaging the ends of the claw parts 11a with an engaging groove 10 formed on the circumferential part of a cylindrical part 8. The engaging groove 10 is equally halved and arranged in the circumferential direction of the cylindrical part 8, and formed in the position for forming a communicating hole 19. The width of the engaging groove 10 is set slightly larger than the width of the claw part 11a. According to this, the sectional area of the part for forming the engaging groove of the cylindrical part 8 can be increased more than when the engaging groove is annularly formed, the reduction in compression strength can be thus suppressed to prevent the breakage of a piston body 1, and the function as a master cylinder can be ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a resin piston for a master cylinder mounted on a vehicle or the like.

[0002]

2. Description of the Related Art An example of this kind of prior art is disclosed in Japanese Utility Model Publication No. 3-27013. This publication discloses a technique in which a piston for a master cylinder is made of a resin material (plastic material).

In this prior art, when a retainer is externally fitted to an end of a resin piston on the side of a hydraulic pressure chamber, a peripheral groove (hereinafter referred to as an engagement groove) for engaging with the retainer is formed on an outer periphery of the piston. The retainer's pawl is engaged with the groove to position and prevent the retainer from coming off.

[0004]

When the retainer is used as a spring receiver for a center valve, the above-mentioned engagement groove is formed in the peripheral wall of the recess at the tip of the piston in which the center valve is housed. However, despite the fact that the concave peripheral wall is a place where the radial cross-sectional area is smaller than other parts of the piston, conventionally the engaging groove is formed in this position in an annular shape, so that the radial cross-sectional area is further increased. Becomes smaller,
This may cause a reduction in the compressive strength of the resin piston. In this case, the piston may be damaged by the hydraulic pressure generated when the master cylinder operates, and the function as the master cylinder may not be maintained.

The present invention has been made in view of the above problems, and provides a resin piston for a master cylinder capable of maintaining a function as a master cylinder by assembling a retainer while minimizing a decrease in the strength of the resin piston. The task is to

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a master cylinder which is slidably fitted into a cylinder hole of a master cylinder, and in which a body defining a hydraulic chamber is formed of a resin material. A resin piston for a cylinder,
The end surface facing the hydraulic pressure chamber has a cylindrical portion that defines a concave portion having an opening and has an engaging groove formed on an outer peripheral portion, and the cylindrical portion is positioned by being engaged with the engaging groove. A resin piston for a master cylinder having a retainer attached to the outer periphery of the portion, wherein the engagement groove is divided into two or more in the circumferential direction of the cylindrical portion, and the resin piston for a master cylinder is provided. Will be resolved.

That is, according to the present invention, the engagement groove formed on the outer peripheral portion of the cylindrical portion for engaging the retainer is divided into two or more in the circumferential direction of the cylindrical portion, and the engagement groove is formed. The reduction of the radial cross-sectional area (that is, the thickness of the cylindrical portion) of the cylindrical portion due to the formation is minimized, and the function as the master cylinder is maintained without lowering the compressive strength.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 to FIG. 5 show a resin piston for a master cylinder according to an embodiment of the present invention. The main body 1 of the piston is formed of a resin material, and in the present embodiment, is configured as a secondary-side piston (slave piston) applied to a tandem-type master cylinder. FIG. 1 shows a state where the main body 1 is pushed in response to the operation of the master cylinder, and shows a moment when a valve body 13 to be described later is seated on a valve seat 16.

Two annular grooves 2 and 3 are formed in a side peripheral portion of the main body 1, and these annular grooves 2 and 3 are inserted into a cylinder hole (not shown) in front of the main body 1 (see FIG. 1). Annular cup seals 4 that define the second and first hydraulic chambers respectively at the middle left and the following, and the rear (the right in the figure, the same hereinafter);
5 is mounted. The first hydraulic chamber is a hydraulic chamber defined between the main body 1 and a primary piston (main piston) not shown, and the second hydraulic chamber is provided between the main body 1 and a closed bottom of the cylinder hole. It is a hydraulic chamber partitioned into. Reference numeral 20 denotes a gate portion for resin injection.

In this embodiment, the main body 1 is formed for a piston of a center valve type master cylinder. That is, at the front end face of the main body 1 facing the second hydraulic chamber, a cylindrical portion 8 that defines a concave portion 7 having an opening 6 is formed, and the concave portion 7 is a valve body of a valve mechanism 9 constituting a center valve. 1
3 is used as a space for accommodating the same.

As is well known, the valve mechanism 9 opens and closes fluid communication between the second hydraulic chamber and a hydraulic fluid reservoir (not shown) in which hydraulic fluid is stored.
, A stem 14 extending into the axial passage 15 of the main body 1, a stopper 17 to which the stem 14 can abut at an end, and a valve body 13 urged in the direction of the valve seat 16. And a metal retainer 11 that covers the opening 6 and supports one end of the valve spring 12. Stopper 17
Penetrates a long hole 18 formed at the axial center portion of the main body 1 and has both ends fixed to the wall surface of a cylinder hole (not shown). The fluid communication between the recess 7 and the second hydraulic chamber is
1 and a communication hole 19 formed in the cylindrical portion 8.
Done through.

In the present embodiment, the retainer 11 has two claw portions 11a bent inward as shown in the figure, and the ends of the claw portions 11a are formed on the outer peripheral portion of the cylindrical portion 8. Groove 1
It is prevented from slipping out by engaging and positioning with zero. Here, the engagement groove 10 is formed in the cylindrical portion 8 in the present embodiment.
Are equally divided into two in the circumferential direction, and are formed at positions where the communication holes 19 are formed as shown in FIG.
The width of the engagement groove 10 is formed slightly larger than the width of the claw portion 11a.

Thus, the cross-sectional area of the portion of the cylindrical portion 8 where the engaging groove is formed can be made larger than that in the case where the engaging groove is formed in a ring shape as in the prior art, and therefore, the compressive strength is increased. To prevent the piston body 1 from being damaged,
Maintaining the function as the master cylinder can be ensured.

If the hole 11b of the retainer 11 is formed in a symmetrical shape with respect to the diameter direction having the claw portion 11a as shown in FIG. 5, when a dedicated jig having a shape matching the hole 11b is used. Since it is possible to supply the retainer 11 while keeping the position of the claw portion 11a constant, the retainer 11
In the automatic assembling step, the claw portion 11a can be securely engaged with the engagement portion 10.

Referring to FIGS. 2 and 4, the radial cross section of the main body 1 in which the long hole 18 is formed has one rib 21 in which the long hole 18 is formed and the other rib 22 orthogonal to each other. It has a substantially cross shape, and the thickness of one rib 21 and the thickness of the other rib 22 are substantially the same. That is, the thickness (d1 + d1) of the rib 21 forming the side wall of the long hole 18 and the thickness d2 of the rib 22 orthogonal to the rib 21 are formed substantially the same.
Thereby, generation of voids (pores) at the time of curing the resin is suppressed, and reduction of the compressive strength is prevented.

Although the embodiments of the present invention have been described above, the present invention is, of course, not limited thereto, and various modifications can be made based on the technical concept of the present invention.

For example, in the above-described embodiment, the engaging groove 10 for engaging the retainer is uniformly formed on the outer periphery of the cylindrical portion 8 in the circumferential direction.
Although it is formed by dividing into three, it is not limited to this, and it is also possible to form by dividing into three or more. In this case, the shape and number of the claw portions 11a of the retainer 11 may be appropriately adjusted.

In the above embodiment, the main body 1 of the piston is configured for the secondary side piston. However, it is of course possible to form the main body 1 for the primary side piston. Further, the present invention is not limited to the center valve type master cylinder, and is applicable to a resin piston for a master cylinder having a recess for accommodating a head portion of a bolt member therein as described in the above-mentioned conventional publication. It is possible.

[0020]

As described above, according to the resin piston for the master cylinder of the present invention, the reduction of the radial cross-sectional area of the cylindrical portion due to the formation of the engagement groove can be minimized. As a result, the compression strength of the piston body is prevented from lowering, and the function as the master cylinder can be maintained.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a resin piston for a master cylinder according to an embodiment of the present invention.

FIG. 2 is a plan view of only a piston main body in FIG.

FIG. 3 is a sectional view taken along the line [3]-[3] in FIG.

FIG. 4 is a sectional view taken along the line [4]-[4] in FIG.

FIG. 5 is a view in the direction of arrows [5]-[5] in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main body 6 Opening 7 Concave part 8 Cylindrical part 9 Valve mechanism 10 Engagement groove 11 Retainer 11a Claw part 13 Valve body 14 Stem 17 Stopper 18 Elongated hole 21 Rib 22 Rib

Claims (3)

[Claims] 1. A master cylinder resin piston, wherein a main body which is slidably fitted into a cylinder hole of a master cylinder and defines a hydraulic chamber in the cylinder hole is formed of a resin material, The end face facing the hydraulic pressure chamber has a cylindrical portion that defines a concave portion having an opening and has an engaging groove formed on an outer peripheral portion, and the cylindrical portion is positioned by being engaged with the engaging groove. A resin piston for a master cylinder, comprising: a retainer attached to an outer periphery of the cylinder; wherein the engagement groove is divided into two or more in a circumferential direction of the cylindrical portion, and is arranged. 2. The device according to claim 1, wherein the recess is used as a space for accommodating a valve element of a valve mechanism for opening and closing fluid communication between the hydraulic chamber and a hydraulic fluid reservoir storing hydraulic fluid. Resin piston for master cylinder. 3. An elongated hole through which a stopper for engaging with a stem extending in the axial direction from the valve body is inserted is formed in a central portion in the axial direction of the main body so as to penetrate in a radial direction. The cross section in the radial direction of the long hole forming portion has a substantially cross shape in which one rib in which the long hole is formed and the other rib are orthogonal to each other, and has a thickness of the one rib and a thickness of the other rib. The resin piston for a master cylinder according to claim 2, wherein the thickness is substantially the same.